Re: [Xen-devel] [PATCH 09/24] libxl: provide libxl__datacopier_*

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2012-04-16 at 18:17 +0100, Ian Jackson wrote:
> General facility for ao operations to shovel data between fds.
> 
> This will be used by the bootloader machinery.
> 
> Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>

Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

> 
> Changes since v6
>  * assert that the ao is non-null on _init.
> ---
>  tools/libxl/Makefile         |    3 +-
>  tools/libxl/libxl_aoutils.c  |  189 
> ++++++++++++++++++++++++++++++++++++++++++
>  tools/libxl/libxl_internal.h |   40 +++++++++
>  3 files changed, 231 insertions(+), 1 deletions(-)
>  create mode 100644 tools/libxl/libxl_aoutils.c
> 
> diff --git a/tools/libxl/Makefile b/tools/libxl/Makefile
> index 5ba144f..6e253b1 100644
> --- a/tools/libxl/Makefile
> +++ b/tools/libxl/Makefile
> @@ -52,7 +52,8 @@ LIBXL_LIBS += -lyajl
> 
>  LIBXL_OBJS = flexarray.o libxl.o libxl_create.o libxl_dm.o libxl_pci.o \
>                         libxl_dom.o libxl_exec.o libxl_xshelp.o 
> libxl_device.o \
> -                       libxl_internal.o libxl_utils.o libxl_uuid.o 
> libxl_json.o \
> +                       libxl_internal.o libxl_utils.o libxl_uuid.o \
> +                       libxl_json.o libxl_aoutils.o \
>                         libxl_qmp.o libxl_event.o libxl_fork.o $(LIBXL_OBJS-y)
>  LIBXL_OBJS += _libxl_types.o libxl_flask.o _libxl_types_internal.o
> 
> diff --git a/tools/libxl/libxl_aoutils.c b/tools/libxl/libxl_aoutils.c
> new file mode 100644
> index 0000000..4c60ad9
> --- /dev/null
> +++ b/tools/libxl/libxl_aoutils.c
> @@ -0,0 +1,189 @@
> +/*
> + * Copyright (C) 2010      Citrix Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU Lesser General Public License as published
> + * by the Free Software Foundation; version 2.1 only. with the special
> + * exception on linking described in file LICENSE.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU Lesser General Public License for more details.
> + */
> +
> +#include "libxl_osdeps.h" /* must come before any other headers */
> +
> +#include "libxl_internal.h"
> +
> +/*----- data copier -----*/
> +
> +void libxl__datacopier_init(libxl__datacopier_state *dc)
> +{
> +    assert(dc->ao);
> +    libxl__ev_fd_init(&dc->toread);
> +    libxl__ev_fd_init(&dc->towrite);
> +    LIBXL_TAILQ_INIT(&dc->bufs);
> +}
> +
> +void libxl__datacopier_kill(libxl__datacopier_state *dc)
> +{
> +    STATE_AO_GC(dc->ao);
> +    libxl__datacopier_buf *buf, *tbuf;
> +
> +    libxl__ev_fd_deregister(gc, &dc->toread);
> +    libxl__ev_fd_deregister(gc, &dc->towrite);
> +    LIBXL_TAILQ_FOREACH_SAFE(buf, &dc->bufs, entry, tbuf)
> +        free(buf);
> +    LIBXL_TAILQ_INIT(&dc->bufs);
> +}
> +
> +static void datacopier_callback(libxl__egc *egc, libxl__datacopier_state *dc,
> +                                int onwrite, int errnoval)
> +{
> +    libxl__datacopier_kill(dc);
> +    dc->callback(egc, dc, onwrite, errnoval);
> +}
> +
> +static void datacopier_writable(libxl__egc *egc, libxl__ev_fd *ev,
> +                                int fd, short events, short revents);
> +
> +static void datacopier_check_state(libxl__egc *egc, libxl__datacopier_state 
> *dc)
> +{
> +    STATE_AO_GC(dc->ao);
> +    int rc;
> +
> +    if (dc->used) {
> +        if (!libxl__ev_fd_isregistered(&dc->towrite)) {
> +            rc = libxl__ev_fd_register(gc, &dc->towrite, datacopier_writable,
> +                                       dc->writefd, POLLOUT);
> +            if (rc) {
> +                LOG(ERROR, "unable to establish write event on %s"
> +                    " during copy of %s", dc->writewhat, dc->copywhat);
> +                datacopier_callback(egc, dc, -1, 0);
> +                return;
> +            }
> +        }
> +    } else if (!libxl__ev_fd_isregistered(&dc->toread)) {
> +        /* we have had eof */
> +        datacopier_callback(egc, dc, 0, 0);
> +        return;
> +    } else {
> +        /* nothing buffered, but still reading */
> +        libxl__ev_fd_deregister(gc, &dc->towrite);
> +    }
> +}
> +
> +static void datacopier_readable(libxl__egc *egc, libxl__ev_fd *ev,
> +                                int fd, short events, short revents) {
> +    libxl__datacopier_state *dc = CONTAINER_OF(ev, *dc, toread);
> +    STATE_AO_GC(dc->ao);
> +
> +    if (revents & ~POLLIN) {
> +        LOG(ERROR, "unexpected poll event 0x%x (should be POLLIN)"
> +            " on %s during copy of %s", revents, dc->readwhat, dc->copywhat);
> +        datacopier_callback(egc, dc, -1, 0);
> +        return;
> +    }
> +    assert(revents & POLLIN);
> +    for (;;) {
> +        while (dc->used >= dc->maxsz) {
> +            libxl__datacopier_buf *rm = LIBXL_TAILQ_FIRST(&dc->bufs);
> +            dc->used -= rm->used;
> +            assert(dc->used >= 0);
> +            LIBXL_TAILQ_REMOVE(&dc->bufs, rm, entry);
> +            free(rm);
> +        }
> +
> +        libxl__datacopier_buf *buf =
> +            LIBXL_TAILQ_LAST(&dc->bufs, libxl__datacopier_bufs);
> +        if (!buf || buf->used >= sizeof(buf->buf)) {
> +            buf = malloc(sizeof(*buf));
> +            if (!buf) libxl__alloc_failed(CTX, __func__, 1, sizeof(*buf));
> +            buf->used = 0;
> +            LIBXL_TAILQ_INSERT_TAIL(&dc->bufs, buf, entry);
> +        }
> +        int r = read(ev->fd,
> +                     buf->buf + buf->used,
> +                     sizeof(buf->buf) - buf->used);
> +        if (r < 0) {
> +            if (errno == EINTR) continue;
> +            if (errno == EWOULDBLOCK) break;
> +            LOGE(ERROR, "error reading %s during copy of %s",
> +                 dc->readwhat, dc->copywhat);
> +            datacopier_callback(egc, dc, 0, errno);
> +            return;
> +        }
> +        if (r == 0) {
> +            libxl__ev_fd_deregister(gc, &dc->toread);
> +            break;
> +        }
> +        buf->used += r;
> +        dc->used += r;
> +        assert(buf->used <= sizeof(buf->buf));
> +    }
> +    datacopier_check_state(egc, dc);
> +}
> +
> +static void datacopier_writable(libxl__egc *egc, libxl__ev_fd *ev,
> +                                int fd, short events, short revents) {
> +    libxl__datacopier_state *dc = CONTAINER_OF(ev, *dc, towrite);
> +    STATE_AO_GC(dc->ao);
> +
> +    if (revents & ~POLLOUT) {
> +        LOG(ERROR, "unexpected poll event 0x%x (should be POLLOUT)"
> +            " on %s during copy of %s", revents, dc->writewhat, 
> dc->copywhat);
> +        datacopier_callback(egc, dc, -1, 0);
> +        return;
> +    }
> +    assert(revents & POLLOUT);
> +    for (;;) {
> +        libxl__datacopier_buf *buf = LIBXL_TAILQ_FIRST(&dc->bufs);
> +        if (!buf)
> +            break;
> +        if (!buf->used) {
> +            LIBXL_TAILQ_REMOVE(&dc->bufs, buf, entry);
> +            free(buf);
> +            continue;
> +        }
> +        int r = write(ev->fd, buf->buf, buf->used);
> +        if (r < 0) {
> +            if (errno == EINTR) continue;
> +            if (errno == EWOULDBLOCK) break;
> +            LOGE(ERROR, "error writing to %s during copy of %s",
> +                 dc->writewhat, dc->copywhat);
> +            datacopier_callback(egc, dc, 1, errno);
> +            return;
> +        }
> +        assert(r > 0);
> +        assert(r <= buf->used);
> +        buf->used -= r;
> +        dc->used -= r;
> +        assert(dc->used >= 0);
> +        memmove(buf->buf, buf->buf+r, buf->used);
> +    }
> +    datacopier_check_state(egc, dc);
> +}
> +
> +int libxl__datacopier_start(libxl__datacopier_state *dc)
> +{
> +    int rc;
> +    STATE_AO_GC(dc->ao);
> +
> +    libxl__datacopier_init(dc);
> +
> +    rc = libxl__ev_fd_register(gc, &dc->toread, datacopier_readable,
> +                               dc->readfd, POLLIN);
> +    if (rc) goto out;
> +
> +    rc = libxl__ev_fd_register(gc, &dc->towrite, datacopier_writable,
> +                               dc->writefd, POLLOUT);
> +    if (rc) goto out;
> +
> +    return 0;
> +
> + out:
> +    libxl__datacopier_kill(dc);
> +    return rc;
> +}
> +
> diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
> index 6ceb362..20c95db 100644
> --- a/tools/libxl/libxl_internal.h
> +++ b/tools/libxl/libxl_internal.h
> @@ -833,6 +833,7 @@ _hidden int libxl__ev_devstate_wait(libxl__gc *gc, 
> libxl__ev_devstate *ds,
>   */
>  _hidden int libxl__try_phy_backend(mode_t st_mode);
> 
> +
>  /* from libxl_pci */
> 
>  _hidden int libxl__device_pci_add(libxl__gc *gc, uint32_t domid, 
> libxl_device_pci *pcidev, int starting);
> @@ -1458,6 +1459,45 @@ int libxl__carefd_close(libxl__carefd*);
>  int libxl__carefd_fd(const libxl__carefd*);
> 
> 
> +/*----- datacopier: copies data from one fd to another -----*/
> +
> +typedef struct libxl__datacopier_state libxl__datacopier_state;
> +typedef struct libxl__datacopier_buf libxl__datacopier_buf;
> +
> +/* onwrite==1 means failure happened when writing, logged, errnoval is valid
> + * onwrite==0 means failure happened when reading
> + *     errnoval==0 means we got eof and all data was written
> + *     errnoval!=0 means we had a read error, logged
> + * onwrite==-1 means some other internal failure, errnoval not valid, logged
> + * in all cases copier is killed before calling this callback */
> +typedef void libxl__datacopier_callback(libxl__egc *egc,
> +     libxl__datacopier_state *dc, int onwrite, int errnoval);
> +
> +struct libxl__datacopier_buf {
> +    /* private to datacopier */
> +    LIBXL_TAILQ_ENTRY(libxl__datacopier_buf) entry;
> +    int used;
> +    char buf[1000];
> +};
> +
> +struct libxl__datacopier_state {
> +    /* caller must fill these in, and they must all remain valid */
> +    libxl__ao *ao;
> +    int readfd, writefd;
> +    ssize_t maxsz;
> +    const char *copywhat, *readwhat, *writewhat; /* for error msgs */
> +    libxl__datacopier_callback *callback;
> +    /* remaining fields are private to datacopier */
> +    libxl__ev_fd toread, towrite;
> +    ssize_t used;
> +    LIBXL_TAILQ_HEAD(libxl__datacopier_bufs, libxl__datacopier_buf) bufs;
> +};
> +
> +_hidden void libxl__datacopier_init(libxl__datacopier_state *dc);
> +_hidden void libxl__datacopier_kill(libxl__datacopier_state *dc);
> +_hidden int libxl__datacopier_start(libxl__datacopier_state *dc);
> +
> +
>  /*
>   * Convenience macros.
>   */
> --
> 1.7.2.5
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel